Centrifugal pump and impeller protector for centrifugal pump

ABSTRACT

The invention relates to a centrifugal pump ( 1 ) that has a suction-side inlet ( 3 ) and at least one pressure-side outlet ( 4 ), wherein a rotatably mounted impeller ( 5 ) for pumping a pump medium from the inlet ( 3 ) to the outlet ( 4 ) and an impeller seat ( 10 ) are arranged in the pump housing ( 2 ). 
     In order to achieve a high degree of sealing and a long service life, the impeller seat ( 10 ) is formed in a ring-shaped impeller protector ( 8 ) which is made from a corrosion-resistant material and is received in the pump housing ( 2 ), wherein an insertion region ( 7 ) of the impeller ( 5 ) is radially surrounded by the impeller protector ( 8 ). 
     This impeller protector ( 8 ) protects the coating against damage to the impeller ( 5 ) in the impeller seat ( 10 ).

FIELD OF THE INVENTION

The invention relates to a centrifugal pump and an impeller protectorfor such a centrifugal pump.

BACKGROUND ART

Centrifugal pumps are used for pumping pump media, which in general arefluids. The pump media enters the centrifugal pump through the inlet andis pumped through the rotation of the impeller to the pressure side andis output under pressure through the outlet. In many cases, the outletis located radially with regard to the impeller, wherein a radial flowis generated by the impeller.

For a good efficiency of the pumps, sufficient sealing is requiredbetween the pressure side and the suction side. For this purpose, theimpeller interacts with an impeller seat that is formed stationarily inthe pump housing. In order to enable a movement of the impeller relativeto the impeller seat, a sealing as complete as possible between theimpeller and the impeller seat requires accurately fitting fabricationand, if necessary, additional sealing. This makes the production of thepump complicated and expensive.

Due to unavoidable manufacturing tolerances, unpleasant grinding noisescan be heard which stop only after a certain running-in time. Thesegrinding noises result from contact between the impeller and theimpeller seat and cause material abrasion at least on one of these twoelements. However, this results also in bypass connections, thus leaks,between the suction side and the pressure side. Also, replacing theimpeller is relatively problematic since usually the new impeller doesnot correspond to the shape of the old impeller seat.

This can also result in damage to a coating of the pump housing or theimpeller seat. This is in particular problematic if the centrifugal pumpis used for corrosive fluids such as, for example, swimming pool water.After long downtimes, in the worst case, rust-induced seizing up of theimpeller in the impeller seat can occur, which entails significantmaintenance work or even requires complete replacement of the pump.

SUMMARY OF THE INVENTION

It is now an object of the invention to eliminate the disadvantages ofthe prior art and in particular to provide a solution by means of whichthe service life of a centrifugal pump can be prolonged and which is inparticular maintenance-friendly, and which provides compensation forplay and improves the efficiency of the centrifugal pump.

Thus, it is provided according to the invention to form the impellerseat in a ring-shaped impeller protector that is made from acorrosion-resistant material and is received in the pump housing,wherein an insertion region of the impeller is radially surrounded bythe impeller protector.

The impeller seat, which through interaction with the impeller seals thepressure side of the pump from a suction side, is therefore not formedintegrally in the pump housing and/or inserted here as an additionalcomponent in a fixed connection, as previously usual in the prior art,but is formed in an additional dynamic element, namely the impellerprotector. The impeller protector can be manufactured with little effortand with relatively high accuracy of fit so that a dynamic compensationof play takes place between the impeller protector and the pump housing.In this manner, a gap between the impeller seat and the impeller can bekept very small so that high efficiency can be achieved. By using acorrosion-resistant material for the impeller protector, protectionagainst corrosion is achieved so that an operation with long downtimesof the centrifugal pump is also possible without any problems, even whencorrosive pump media are used. If due to signs of wear, replacement ofthe impeller and/or impeller seat is required, the impeller protectorcan be replaced in a relatively simple manner so that amaintenance-friendly centrifugal pump with a long service life isobtained. Via the impeller protector, a relatively great eccentricitycan be compensated. This results in easier mounting of the pump withsubsequent smooth running and a high degree of tightness.

It is particularly preferred here that the impeller is radially andaxially guided in the impeller protector. Thus, the position of theimpeller is very precisely predefined by the impeller protector. Theimpeller protector can comprise a radially inward protruding collarwhich, so to speak, serves as an axial end stop for the impeller andforms a portion of the impeller seat. Thereby, a long sealing gap andthus good sealing is obtained.

In a preferred configuration, the impeller rests with a front sideagainst the end stop of the pump housing. The end stop can be formed,for example, as radially and circumferentially extending, inwardlyprotruding web of the pump housing against which the impeller protectorrests. The axial position of the impeller protector within the pumphousing is therefore clearly defined. At the same time, with theimpeller protector resting against the end stop, a first sealing betweenthe pump housing and the impeller protector is already obtained. Therebyit is prevented that the pump medium bypasses the impeller protector.

Preferably, the front side of the impeller protector is chamfered orrounded at least at a radial outer edge. This makes inserting theimpeller protector into the pump housing easier. In addition, this hasmanufacturing-related advantages since geometrical over determinacybetween the pump housing and the impeller protector is avoided.

In a particularly preferred configuration, the impeller protectorcomprises a plastic material, in particular polyoxymethylene (POM) orpolytetrafluoroethylene (PTFE). Suitable as a plastic material are inparticular thermoplastic plastics. Such plastics possess high thermalstability and absolute corrosion resistance. Moreover, plastics exhibitless water absorption and can be processed in a simple manner. POM andPTFE are characterized by high strength, sufficient hardness andstiffness, and exhibit high abrasion resistance and a low frictioncoefficient. Between the impeller and the impeller seat or the impellerprotector, a friction pairing can then be formed in which the impellerslides on the impeller seat or an inner side of the impeller protector.Due to the material of the impeller protector, only minor frictionlosses occur which play only a minor role with regard to the advantagesachievable through good sealing between the impeller seat and theimpeller. Overall, a centrifugal pump with very high efficiency isobtained in this manner.

For sealing and dynamic movement compensation between the impellerprotector and the pump housing, a radial seal can be arranged betweenthe impeller protector and the pump housing. The radial seal is usuallyformed as a ring seal and prevents a bypass connection or leakagebetween the impeller protector and the pump housing, even if theimpeller protector has radial play, thus is movable with respect to thepump housing.

It is particularly preferred here that the radial seal has a sealing lipthat is inclined with respect to an axial direction and rests with asuction-side surface against the pump housing or the impeller protector.On the one hand, this sealing lip, for example a “Viton rubber lip”serves for compensating the play between the impeller protector and thepump housing, and, on the other, for reliable sealing. With the inclinedformation of the sealing lip it is achieved that by the pressure of thepump medium on the pressure side, the sealing lip is pressed against thepump housing or the impeller protector so that with increasing pressure,the sealing effect of the seal is improved at the same time. A radialgap between the pump housing and the impeller protector, which gap, forexample, is advantageous for compensating the play, can then be coveredby the radial seal with the sealing lip without any problems so thatsufficient centering between the impeller and the pump housing or theimpeller protector is possible.

For securing the position in the axial direction, the radial seal can beheld in an annular groove which is in particular formed in acircumferential surface of the impeller protector. Such an annulargroove can be generated in a relatively simple manner, and wheninserting the impeller protector into the pump housing, for example, itprovides already for a defined position of the radial seal. Assemblingthe centrifugal pump is therefore simplified.

Preferably, a groove opening of the annular groove is smaller than thegroove bottom, wherein the annular groove has in particular side flanksthat are inclined toward each other. Thereby, the radial seal is held inthe annular groove by means of a form-locking connection. At the sametime, a high degree of sealing is obtained between the radial sealwithin the annular groove.

Preferably, the radial seal between the impeller protector and the pumphousing is preloaded. The radial preload can be generated, for example,by deforming the sealing lip. Thereby, a friction-locked fit of theimpeller protector in the pump housing can be generated. At the sametime, the preload of the radial seal ensures sufficient sealing even incases where the impeller protector is slightly offset with respect tothe pump housing so as to compensate the play. A radial air gap betweenthe pump housing and the impeller protector is therefore reliably sealedby the radial seal.

The aforementioned object is achieved by an impeller protector that isring-shaped and comprises a corrosion-resistant material, in particularplastic, wherein an impeller seat for an impeller is formed in theimpeller protector. The configurations explained in connection with thecentrifugal pump and the resulting advantages also apply analogously, ofcourse, to the impeller protector.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features, details and advantages of the invention arise from thefollowing description of exemplary embodiments based on the drawings. Inthe figures:

FIG. 1 shows a centrifugal pump in partially cut, spatial illustration,

FIG. 2 shows a cut-out from FIG. 1,

FIG. 3 shows a detail from FIG. 2, and

FIG. 4 shows an impeller protector in a spatial illustration.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a centrifugal pump 1 with a multi-part pump housing 2. Thepump housing 2 has an inlet 3 and a radial outlet 4. An impeller 5 whichis connected to a motor shaft 6 is rotatably held within the pumphousing 2.

An insertion region 7 of the impeller 5 extends into a ring-shapedimpeller protector 8. The impeller protector 8 has a radially inwardfacing circumferential collar 9 and forms an impeller seat 10 for theimpeller 5. For this purpose, the impeller 5 is slidingly guided in theimpeller seat 10 or on the inner surfaces of the impeller protector 8 sothat the pump medium such as, for example, swimming pool water that ispumped from the inlet 3 to the outlet 4 cannot flow between the impellerprotector 8 and the impeller 5, but is radially carried along by theimpeller 5 and thereby gets into a pressure channel 11 and from there tothe outlet 4.

The impeller 5 is radially and axially guided with regard to the pumphousing 2 by the impeller protector 8. In addition to centering and tocompensating a play, the impeller protector 8 also enables good sealingbetween the suction side and the pressure side and, at the same time,only minor friction losses. Here, the impeller protector 8 is formedfrom plastic such as, for example, POM or PTFE and, accordingly, iscorrosion-resistant. Therefore, there is no concern for rust-inducedseizing up of the impeller 5 in the impeller seat 10, not even duringlong downtimes.

The impeller protector 8 rests with a front side 12 against an end stop13 of the pump housing 2, which end stop is formed by a radially inwardprotruding circumferential web of the pump housing 2. Thus, the axialposition of the impeller protector 8 within the pump housing 2 isdetermined by a form-locking connection. In this manner it is achievedthat the impeller protector 8 rests in a secure and tight manner againstthe pump housing 2.

FIG. 2 illustrates in an enlarged view the arrangement of the impellerprotector 8 within the pump housing 2 and the impeller 5. The impellerseat 10 is the contact surface between the insertion region 7 of theimpeller 5 and a radial inner side of the impeller protector 8 with anaxial upper side of the collar 9. Thereby, a relatively large contactarea is obtained, through which good sealing is achieved. At the sametime, friction is kept low by the material used for the impellerprotector 8 so that overall a high degree of efficiency can be achieved.

A radial seal 15 that radially seals the impeller protector with respectto the pump housing 2 is arranged in an annular groove 14 of theimpeller protector 8. On its radial outside, the radial seal 15 has asealing lip 16 which rests with a suction-side surface 17 against thepump housing 2. Thus, the sealing lip 16 extends at an angle relative tothe axial direction of the motor shaft 6. Thereby, a gap 18 is bridgedby the radial seal 15 or the sealing lip 16, which gap is annularlyformed between the impeller protector 8 and the pump housing 2. Thus,the impeller protector 8 can be aligned with regard to its radialposition within the pump housing 2 and therefore can compensatetolerances between the position of the impeller 5 and the pump housing2. As a result, the impeller protector 8 can always be accuratelycentered with respect to the impeller 5. By radially bracing the radialseal 15 between the impeller protector 8 and the pump housing 2, aholding force can be generated by the radial seal 15. This results in afriction-locked fastening of the impeller protector 8 in the pumphousing 2.

As is shown in particular in FIG. 3, a groove opening 19 is smaller thana groove bottom 20. This is achieved through side flanks 21, 22 of thering groove 14 which are inclined toward each other. Through this, theradial seal 15 can be received within the annular groove 14 in aform-locking manner so that the position of the radial seal 15 withrespect to the impeller protector 8 is clearly defined. Also, a largesealing area is obtained between the radial seal 15 and the impellerprotector 8, and thus good sealing is achieved.

A radial outer edge 23 of the front side 12 of the impeller protector 8has a chamfer which makes inserting the impeller protector 8 into thepump housing 2 easier. In addition, geometrical over determinacy isavoided in this manner.

FIG. 4 shows the impeller protector 8 in a three-dimensionalillustration. The radial seal 15 is received in the annular groove 14which is formed in the circumferential surface of the impeller protector8. The circumferentially extending collar 9, which represents a portionof the impeller seat 10, is assigned to the front side 12 so that asufficient guide surface within the impeller protectors is available forthe impeller 5 in the radial and axial directions.

Through the impeller protector, flexible sealing of the impeller seat,thus with respect to the impeller, is obtained. This leads to maximumsealing, wherein disadvantageous bypasses between a pressure side and asuction side are avoided. At the same time, this provides wearprotection since a coating of the pump housing is protected by theimpeller protector. Direct contact between the impeller and the pumphousing is avoided due to the impeller protector. With the impellerbeing slidingly mounted, the impeller protector enables an impellermovement with very low friction. In addition, rust-induced seizing up ofthe impeller in the pump housing is prevented by producing the impellerprotector from a rustproof material such as, for example, a plasticmaterial. By a radial seal, in particular with a sealing lip, a highdegree of tightness is also achieved between the impeller protector andthe pump housing, wherein compensation of play is ensured at the sametime.

Through the impeller protector, almost wear-free rotating of theimpeller within the pump housing is achieved, wherein the pump housingcan be completely coated. Because of the good sealing, the efficiency ofthe pump is improved once again. Another advantage arises duringmaintenance of the centrifugal pumps. For example, by replacing theimpeller protector, a simple replacement of the impeller seat ispossible without coated surfaces of the pump housing getting damaged.Also, no unpleasant grinding noises occur during a first start-up, butinstead, a quiet and pleasant operation is achieved.

The centrifugal pump according to the invention can also be used withcorrosive pump media such as, for example, swimming pool water. It ispossible here to produce the pump housing as a gray iron casting and tocoat all surface that come into contact with the pump medium so thatgood protection of the gray iron material, which as such is susceptibleto corrosion, is achieved. Thus, the range of use of these pumps issignificantly expanded.

REFERENCE LIST

-   1 Centrifugal pump-   2 Pump housing-   3 Inlet-   4 Outlet-   5 Impeller-   6 Motor shaft-   7 Insertion region 7-   8 Impeller protector-   9 Collar-   10 Impeller seat-   11 Pressure channel-   12 Front side-   13 Web-   14 Annular groove-   15 Radial seal-   16 Sealing lip-   17 Suction-side surface-   18 Gap-   19 Groove opening-   20 Groove bottom-   21 Side flank-   22 Side flank-   23 Outer edge

The invention claimed is:
 1. A centrifugal pump (1) comprising a pumphousing (2) that has a suction-side inlet (3) and at least onepressure-side outlet (4), wherein a rotatably mounted impeller (5) forpumping a pump medium from the inlet (3) to the outlet (4) and animpeller seat (10) are arranged in the pump housing (2), characterizedin that the impeller seat (10) is formed in a ring-shaped impellerprotector (8) which is made from a corrosion-resistant material and isreceived in the pump housing (2), wherein an insertion region (7) of theimpeller (5) is radially surrounded by the impeller protector (8), andfurther wherein a radial seal (15) is arranged between the impellerprotector (8) and the pump housing (2).
 2. The centrifugal pumpaccording to claim 1, characterized in that the impeller (5) is radiallyand axially guided in the impeller protector (8).
 3. The centrifugalpump according to claim 1, characterized in that the impeller protector(8) has a radially inward protruding collar (9).
 4. The centrifugal pumpaccording to claim 1, characterized in that the impeller protector (8)rests with a front side (12) against an end stop (13) of the pumphousing (2).
 5. The centrifugal pump according to claim 4, characterizedin that the front side (12) of the impeller protector (8) is chamferedor rounded at least at one outer edge (23).
 6. The centrifugal pumpaccording to claim 1, characterized in that the impeller protector (8)comprises a plastic material.
 7. The centrifugal pump according to claim1, characterized in that the radial seal (15) has a sealing lip (16)which is inclined with respect to an axial direction and rests with asuction-side surface (17) against the pump housing (2) or the impellerprotector (8).
 8. The centrifugal pump according to claim 1,characterized in that an annular groove (14), in which the radial seal(15) is held, is formed in a circumferential surface of the impellerprotector (8).
 9. The circumferential pump according to claim 8,characterized in that a groove opening (19) of the annular groove (14)is smaller than a groove bottom (20), wherein the annular groove (14)has in particular side flanks (21, 22) which are inclined toward eachother.
 10. The centrifugal pump according to claim 1, characterized inthat the radial seal (15) is preloaded between the impeller protector(18) and the pump housing (2).
 11. An impeller protector for acentrifugal pump according to claim 1, which impeller protector isring-shaped and comprises a corrosion-resistant material, wherein animpeller seat (10) for an impeller is formed in the impeller protector(8).
 12. The centrifugal pump according to claim 6, wherein the plasticmaterial is polyoxymethylene or polytetrafluoroethylene.
 13. Theimpeller protector for a centrifugal pump according to claim 11, whereinthe corrosion-resistant material is plastic.